Hyperselective carbon membranes for precise high-temperature H2 and CO2 separation

More than 90% of the world’s hydrogen (H₂) is produced from fossil fuel sources, which requires energy-intensive separation and purification to produce high-purity H₂ fuel and to capture the carbon dioxide (CO₂) by-product. While membranes can decarbonize H₂/CO₂ separation, their moderate H₂/CO₂ selectivity requires secondary H₂ purification by pressure swing adsorption. Here, we report hyperselective carbon molecular sieve hollow fiber membranes showing H₂/CO₂ selectivity exceeding 7000 under mixture permeation at 150°C, which is almost 30 times higher than the most selective nonmetallic membrane reported in the literature. The membrane is able to maintain an ultrahigh H₂/CO₂ selectivity over 1400 under mixture permeation at 400°C. Pore structure characterization suggests that highly refined ultramicropores are responsible for effectively discriminating the closely sized H₂ and CO₂ molecules in the hyperselective carbon molecular sieve membrane. Modeling shows that the unprecedented H₂/CO₂ selectivity will potentially allow one-step enrichment of fuel-grade H₂ from shifted syngas for decarbonized H₂ production.